Enjoy hot water on your boat with a dependable Seaward Marine Water Heater.Heat water dockside with 120V AC power or when underway, using engine heat. These water heaters feature an ignition-protected design, cladded aluminum tanks, and dual-wall heat exchangers. To facilitate installation, heat exchanger ports are offered with a choice of two configurations—either located on the same side where the cold in/hot out ports are located, or on the opposite or "rear" side of the unit. For the outer case, choose between stainless steel, galvanized steel, or epoxy-coated aluminum. To protect against galvanic corrosion and extend tank life, use of a magnesium anode is highly recommended. For more information, see the Seaward Water Heater Owner's Manual.Key Features Choice of stainless steel, galvanized steel or epoxy-coated aluminum caseChoice of front- or rear-located heat exchanger ports to conform to installation requirements6-, 11, 20-gallon capacities20-Gallon heater (Model 11656618) does not include an engine water heat exchanger